A hydrogenated ring-opening polymer of dicyclopentadiene or the like is a cycloolefin polymer that exhibits excellent transparency, low birefringence, excellent formability (processability), and the like, and is used as a material that can be applied to various applications such as optical applications.
However, a hydrogenated ring-opening polymer of dicyclopentadiene or the like is normally obtained in the form of an amorphous polymer that has an atactic structure with random tacticity, and may exhibit insufficient heat resistance, mechanical strength, solvent resistance, and the like depending on the application.
In order to improve the performance of such a hydrogenated ring-opening polymer, it has been proposed to provide a hydrogenated ring-opening polymer of dicyclopentadiene or the like with crystallinity.
For example, Patent Literature 1 discloses that a ring-opening polymer having crystallinity is obtained by subjecting dicyclopentadiene to ring-opening polymerization using a polymerization catalyst that mainly includes a Group 6 transition metal compound (i.e., a compound that includes a transition metal that belongs to Group 6 in the periodic table) that is substituted with a specific substituent, and a hydrogenated ring-opening polymer having crystallinity is obtained by hydrogenating the carbon-carbon double bonds included in the ring-opening polymer using a hydrogenation catalyst. Patent Literature 2 discloses that a ring-opening polymer having syndiotacticity is obtained by subjecting dicyclopentadiene to ring-opening polymerization using a polymerization catalyst that mainly includes a Group 6 transition metal compound that includes an imido ligand, and a syndiotactic hydrogenated ring-opening polymer having crystallinity in which the ratio of racemo diads is 51% or more, is obtained by hydrogenating the carbon-carbon double bonds included in the ring-opening polymer using a hydrogenation catalyst.
The melting point of these crystalline hydrogenated dicyclopentadiene ring-opening polymers is 260 to 290° C. However, the glass transition temperature of a hydrogenated dicyclopentadiene ring-opening polymer is about 100° C. irrespective of whether the hydrogenated dicyclopentadiene ring-opening polymer is crystalline or amorphous. Therefore, when a crystalline hydrogenated dicyclopentadiene ring-opening polymer is heated to a temperature equal to or higher than 100° C., the amorphous domain of the resin undergoes thermal relaxation. Accordingly, a formed article produced using a crystalline hydrogenated dicyclopentadiene ring-opening polymer may change in mechanical strength or heat resistance at about 100° C., whereby an increase in coefficient of linear expansion may occur, or deflection may occur even under a low load, for example.
Patent Literature 3 discloses that a ring-opening polymer having syndiotacticity is obtained by subjecting tetracyclododecene to ring-opening polymerization using a specific ring-opening polymerization catalyst that mainly includes a Group 6 transition metal compound that includes an imido ligand, and an amorphous hydrogenated tetracyclododecene ring-opening polymer is obtained by hydrogenating the carbon-carbon double bonds included in the ring-opening polymer. Patent Literature 3 discloses that, when tungsten hexachloride is used as the polymerization catalyst, the resulting hydrogenated tetracyclododecene ring-opening polymer has a melting point (280° C.), but does not have a glass transition temperature (i.e., a semi-crystalline resin is obtained).